Disposable garments, such as infant and children's diapers, swim wear and training pants, as well as adult incontinence garments, conventionally include materials that are joined together and connected using a bonding process. For example, a training pant or other pant-type garment may have a front side panel and a back side panel that are bonded together at a side seam to provide a complete side panel. The side panels are typically connected at the side seam using an ultrasonic process.
The ability to form strong ultrasonic bonds using conventional processes is limited by several factors, including the process converting speeds or production line speeds, bonding time or dwell time, and the thickness and/or basis weight of the materials being bonded.
For particular materials, such as spunbond laminate materials, as the production line speed increases, the dwell time decreases. Consequently, the strength of the ultrasonic bond decreases resulting in insufficient bond strength. Thus, insufficient bond strength may severely limit potential product converting speeds. Additionally, adhesives used to bond spunbond materials and the elastic filaments or fibers used to make such materials elastomeric may inhibit the effectiveness of conventional ultrasonic bonding processes.
Attempts to improve the ultrasonic bonding process have focused on the mechanics of the ultrasonic horn, such as, for example, increasing the energy available from the ultrasonic horn by increasing the horn vibrational amplitude or other design features. However, the mechanical design of the ultrasonic horn may limit the maximum energy that can be delivered by the ultrasonic system to the materials being bonded, thus making it difficult to further enhance the bonding capability of the ultrasonic bonder by modifying the ultrasonic horn and/or the amplifier design. Further attempts to improve ultrasonic bond strength, without sacrificing speed, have included preheating the materials to be bonded prior to the bonding process. However, with heat sensitive materials, such processes cannot be used.
Thus, there is a need for an ultrasonic bonding process that provides sufficient bond strength at increased production line speeds and corresponding decreased dwell times.